Clamp mechanism with trailing arm control

ABSTRACT

Clamp mechanism including a pair of opposed clamp members movably mounted on a frame. The clamp members are movable toward and away from each other to effect clamping and release of a load, and are movable in the same direction on the frame, to one or the other side, for the purpose of side shifting a load. A fluid-pressure operated ram is connected to each clamp member to move it under power. Hydraulic circuit means connects a source of fluid under pressure with the rams, this circuit means on side shifting connecting the rams in series with one dumping into the other. The hydraulic circuit means includes a pair of valves, one associated with each clamping member. One valve is actuated by the clamp member which is trailing on side shifting in one direction to stop the supply of pressure fluid to the rams prior to the ram for the trailing clamp member reaching the end of its stroke. A valve associated with the other clamp member performs a similar function with the other clamp member moving as a trailing member on side shifting.

United States Patent [1 1 Didtel et al.

[ June 12, 1973 CLAMP MECHANISM WITH TRAILING ARM CONTROL Inventors:Stuart R. Didtel, Gresham; Harlan D.

Olson, Portland, both of Oreg.

Assignee: Cascade Corporation, Portland,

Oreg.

Filed: Aug. 13, 1971 Appl. No.: 171,451

U.S. Cl. 214/653, 214/730 Int. Cl 1366f 9/14 Field of Search 214/653,730

[56] References Cited UNITED STATES PATENTS l/l965 Quayle 214/653 2/1966Romine 214/730 Primary ExaminerRobert G. Sheridan AssistantExaminer-George F. Abraham Attorney-Kolish, Hartwell & Dickinson [57]ABSTRACT Clamp mechanism including a pair of opposed clamp membersmovably mounted on a. frame. The clamp members are movable toward andaway from each other to effect clamping and release of a load, and aremovable in the same direction on the frame, to one or the other side,for the purpose of side shifting a load. A fluid-pressure operated ramis connected to each clamp member to move it under power. Hydrauliccircuit means connects a source of fluid under pressure with the rams,this circuit means on side shifting connecting the rams in series withone dumping into the other. The hydraulic circuit means includes a pairof valves, one associated with each clamping member. One valve isactuated by the clamp member which is trailing on side shifting in onedirection to stop the supply of pressure fluid to the rams prior to theram for the trailing clamp member reaching the end of its stroke. Avalve associated with the other clamp member performs a similar functionwith the other clamp member moving as a trailing member on sideshifting.

4 Claims, 4 Drawing Figures w tit X1,

CLAMP MECHANISM WITH TRAILING ARM CONTROL This invention relatesgenerally to clamp mechanism including a pair of opposed clamp membersmounted on a frame movable toward and away from each other for thepurpose of clamping onto and releasing a load. Such an organization ischaracteristic of a lift truck attachment utilized in clamping ontocartons and the like, to enable subsequent lifting of the cartons andtheir movement from one location to another.

Clamp mechanism of the type described may conventionally include afluid-pressure operated ram associated with each clamp member for movingit under power. Hydraulic circuit means connects a source of fluid underpressure with these rams. With one adjustment of such circuit means, therams are actuatable to move the clamp members toward and away from eachother for the purpose of gripping onto and releasing a load. Withanother type of adjustment, the rams are actuatable to move the clampmembers in the same direction, either to one or to the other side of theframe, for the purpose of side shifting a load.

This invention is directed to the problem of maintaining at all timesfull clamping pressure on the load dur ing side shifting. Furtherexplaining, it has been noted that with loads having a side to sidedimension which is somewhat less than the maximum size of load that canbe handled, what limits side shifting in any given direction is the ramwhich moves the trailing clamp member reaching the end of its stroke,for example, by the piston of the ram bottoming out in the ramscylinder. The hydraulic circuit which is provided to deliver pressurefluid to the rams may be constructed so as to stop the supply ofpressure fluid to the ram for the leading clamp member immediately onsuch bottoming out occurring. From a hydraulic standpoint, this shouldprevent relaxation of clamping pressure in the load at the end of sideshifting. However, as a practical matter, such is not the case sincewith relatively heavy and with certain types of clamp constructions,momentum tends to cause the leading member to move away from thetrailing one at the end of a side shifting cycle. This results inmomentary loss of clamping pressure, and any such loss of clampingeffort obviously is detrimental to the overall operation of the clamp.

This invention has as its general object the provision of clampmechanism for handling loads with means whereby sustained clampingpressure is maintained on all load sizes during side shifting.

More particularly, this invention comprises a novel organization ofopposed clamp members, and rams for moving these under power, with meansoperable hydraulically to stop ram actuation prior to the ram for thetrailing clamp member on side shifting reaching the end of its stroke.

A more specific object is to provide, in an attachment such as a lifttruck attachment, opposed clamp mem bers for clamping onto a load, andvalves means mounted on the frame of the attachment operated by portionsmovable with the clamp members operable to make adjustments in thehydraulic circuit means supplying pressure fluid to the rams, wherebythe ram for the trailing clamp member is prevented from reaching the endof its stroke.

Yet another object is to provide clamp mechanism, such as might beprovided in an attachment for a lift truck, with valve means operated bythe clamp members preventing the supply of pressure fluid to a ram whenthe ram for the trailing clarnip member nears the end of its stroke.

These and other object and advantages of the invention will become morefully apparent from the accompanying description, to be read inconjunction with the accompanying drawings wherein:

FIG. 1 is a view, in simplified form, illustrating a lift truck equipedwith a mast, and clamp mechanism elevatable on such mast, ascontemplated by an embodiment of the invention;

FIG. 2 is a view on a somewhat enlarged scale, viewing the back of theclamp mechanism or attachment;

FIG. 3 is a top view showing portions of the attachment as illustratedin FIG. 2, and

FIG. 4 is a schematic drawing illustrating the hydraulic circuit meanswhich, in conjunction with two fluid pressure operated rams, isutilized. to effect controlled movement of the clamp members in theclamp mechanism.

Referring now to the drawings, and first of all more particularly toFIG. 1, shown at 10 is a lift truck equiped at the forward end thereofwith a mast assembly 12 carrying clamp mechanism generally shown at 14mounted on the carriage of the mast assembly. The

most assembly may be extended and the carriage raised on the mastassembly to effect lifting of a load clamped onto by clamp mechanism 14.As will be hereinafter described, the clamp mechanism includes a pair ofopposed clamp members mounted for movement on'a frame for movementtoward and away from each other, for the purpose of clamping onto andreleasing a load. The clamp members are moved in the same direction, toone side of theframe or to the other, to effect side shifting of theload. Fluid pressure operated rams power such movement of the clampmembers, such being supplied with pressure fluid from a source ofpressure fluid located on the truck and connected through flexible hosesto the rams which form part of the clamp mechanism.

Referring now to FIGS. 2 and 3, the frame of the clamp mechanism isindicated at 16. The clamp members, indicated partially at 18 and 20,are carried on the frame with such projecting forwardly of the frame.Guide tubes, such as those shown at 22 in the frame, slidably receiveguide rods which are secured to the clamp member, thus to mount theclamp members in place on the frame while providing for movement in eachof the clamp members along the frame to one or the other side thereof.End plates 24 join the guide tubes and make a rigid unit of the frame16.

Indicated at 30 is a fluid pressure operated ram having the cylinder end30a thereof joined by fastener 32 to the end plate 24 shown at the rightof the figure in FIG. 2. The rod of the ram, given the reference numeral30b is joined by a fastener 34 to the clamp member 18 as shown at theleft in FIG. 2.

Ram 30 is a double acting ram, and is shown in FIG. 2 at nearly the endof a completed stroke for the ram,

i.e., its contraction stroke. The end of the stroke may trails memberwhen moved left to right, as is performed with contraction of ram 30.

Also shown in FIG. 2 is a ram 38 which has its cylinder end 38aconnected by fastener 40 to the left end plate 24 in FIG. 2. The rod 38bof the ram is connected by a fastener 42 to clamp member 20 at the rightof FIGS. 2 and 3.

With clamp member 20 moved from right to left, such trails clamp member18 on side shifting. Such movement is produced with contraction of ram38. Again, the end of the contraction stroke is determined by the pistonin the ram striking the rams end wall, or alternatively by somemechanical means externally of the ram which prevents furthercontraction.

To grip onto a load the two clamp members are brought toward each otherby directing pressure fluid to the rams 30, 38 in such a manner thatboth are contracted simultaneously. To release the load, both rams areextended simultaneously, through proper channeling of fluid underpressure. Side shifting to the left is accomplished by extending ram 30simultaneously with contracting of ram 38, and side shifting to theright is produced under power by extending ram 38 simultaneously withcontracting of ram 30.

With larger loads, where the clamp members are spread relatively farapart, and assuming side shifting to the right, the amount of sideshifting will not be limited by ram 30 nearing the end of itscontraction stroke, since ram 38 will reach the end of its extensionstroke well before this occurs. With ram 38 moving the leading clampmember on side shifting to the right, and on ram 38 reaching the end ofits extension stroke, there is no relaxing of clamping pressure.However, with narrower loads, and absent the concepts of this invention,side shifting to the right must cease upon ram 30 reaching the end ofits contraction stroke. Even assuming that the supply of fluid underpressure to the rams is stopped immediately at this time, there is apossibility of some relaxation of clamping pressure on this happening,due to momentum tending to force the load and leading clamp memberslightly ahead of the mechanically and abruptly stopped trailing clampmember. It should be obvious that the same considerations are involvedwith side shifting to the left.

Reference is now made to FIG. 4 where the hydraulic circuit connectingthe source of fluid under pressure on the truck with the rams 30, 38 isillustrated. As shown in the figure, at 50 is a multiple pilot checkvalve assembly having a pair of ports 52, 54 in a housing 56 used inconnecting the valve assembly with the source of fluid under pressure.The latter is shown at 58, and includes a pump 59 and a sump 60. Theconnection is made by way of conduits 62, 64, which may be flexiblehoses, since they extend from the valve assembly which is located on theattachment to a control valve 66 located on the lift truck. The controlvalve is a three position valve adjustable from a neutral position(shown), wherein conduits 62, 64 are closed off by the valve, to oneposition where conduit 68 leading to the pressure side of pump 59connects with conduit 62 to supply pressure fluid thereto with conduit64 being connected to a conduit 70 exhausting into the sump. The valvein another position of adjustment connects conduit 68 to conduit 64,with conduit 62 connecting through the valve to conduit 70 and the sump.

The check valve assembly also includes ports 72, 74 connected by conduit76 and conduit 78, respectively,

to the cylinder end of rams 38, 30, respectively. The rod ends of theserams are connected by conduits 80 and 82, respectively, and conduit 84,to a port 86 in valve assembly 50. Adjustable restrictors in conduits80, 82 are shown at 83, 85.

The pilot check valve assembly includes an internal passage 90connecting with conduit 64, and also connecting with ports 72 and 74through ball controlled ports 92, 94. With pressure fluid in passage 90,ports 92, 94 open, with fluid under pressure being fed to ports 72, 74.Fluid under pressure in passage 90 also operates a piston 96, whichmoves downwardly to unseat a ball 97 closing port 98.

Internal passage in the valves assembly connects with port 52 and port98. With unseating of ball 97, port 98 connects with port 86 and conduit84.

With pressure fluid introduced to passage 100 through port 52, such willunseat ball 97 to connect passage 100 with port 86. The pressure fluidalso acts upon pistons 102, 104 to unseat the balls closing ports 92,94, thus to connect ports 72, 74 with port 54.

The pilot check valve assembly, conduits 76, 78, and conduits 62, 64,constitute a hydraulic system in the hydraulic circuit illustratedutilized in actuating the rams to produce clamping and release movementin the members. During this type of operation, the rams 38, 30 areconnected in parallel so to speak, with each receiving pressure fluidfrom one of the conduits 62, 64, and exhausting fluid from the oppositeend of the ram to the other of the conduits 62, 64.

Further explaining, to bring the clamp members together, control valve66 is adjusted to introduce pressure fluid to conduit 62 and connectconduit 64 to exhaust line 70. This results in fluid under pressurebeing directed through ports 98 and 86 to conduits 84, 80, 82, to causecontraction of the rams. Fluid exhausts through conduits 76,78 and ports72, 74 and through passage 90. To cause the clamping members to moveapart, the control valve is adjusted to direct pressure fluid to conduit64 and connect conduit 62 to exhaust conduit 70. The pressure fluid isdirected by the check valve assembly to conduits 76, 78 to causeextension of the rams 38, 30, with fluid exhausting from the oppositeends of the rams through port 84 and conduit 62.

To produce side shifting movement of the clamp members, a control valve106 is utilized, mounted on the truck, which has conduits 108, 110connected thereto connecting with the pump and sump, respectively. Thecontrol valve is a three position valve, similar to valve 66,controlling the flow into and out of conduits 112, 114.

Conduit 114 connects through a valve 118 with a conduit 116 which joinswith previously mentioned conduit 78 to connect with the cylinder end ofram 30.

Valve 118 includes a housing 118a, and as can be seen in FIGS. 2 and 3,such housing is mounted on he frame of the clamp mechanism in a positiongenerally on top of the frame, through a bracket 120. Referring to FIG.4, the valve includes two ports 118b and 1180, such normallycommunicating with each other through internal passage 119 in the valvehousing. Port 1l8b is closed when a ball 118d is moved to the left inFIG. 4 to come up against the port.

The ball is mounted within a reciprocable plunger, also referred to asan actuator or sensor, shown at 122. The plunger includes telescopingparts 122a, 122d urged apart to a limit position by a spring 1220.

Referring to FIGS. 2 and 3, the valve housing is mounted so that plunger122 has a protruding end which is in the path of an angle piece 124secured to clamp whereby such angle piece is in effect part of the clampmember. On the clamp member being moved to the left in FIGS. 2 and 3, byram 38, to a position where the ram is near the end of its contractionstroke, angle piece or portion 124 engages the plunger, and then shiftsit whereby the ball described closes port 118b. With the clamp membermoved to the right to release plunger 122, and pressure fluid fedthrough conduit 114 to port 118e, such pressure fluid acts upon theplunger and ball to open up port 118b.

Conduit 128 is shown in FIG. 4 which connects a valve 134 with conduit76. Associated with valve 134 is a protruding plunger 130 acted upon byangle piece 132 (see FIG. 2). Conduit 112 discussed earlier alsoconnects with valve 134. Valve 134, plunger 130, and angle piece 132perform a function for clamp member 18 corresponding to the functioningjust described of valve 118, plunger 122, and angle piece 124 for clampmember 20.

Considering now how side shifting is performed, to produce side shiftingto the left in FIG. 4 control valve 106 is adjusted to introducepressure fluid to conduit 114, and to connect conduit 112 to exhaustconduit 110. Pressure fluid flowing through conduit 114 and valve 118 isintroduced through conduit 116 to the cylinder end of ram to produceextension of the ram and movement to the left of clamp member 18, thisclamp member being the leading clamp member. Fluid exhausting from therod end of ram 30 passes through conduit 82 into conduit 80 and to therod end of ram 38, to produce contraction of this ram. Fluid exhaustsfrom the cylinder end of ram 38 through conduit 76, conduit 128 intoconduit 112. It will be noted that the rams in effect are connected inseries with the exhaust from one ram entering into the other to actuatethis other ram.

The trailing clamp member with side shifting movement to the left isclamp member 20. On ram 38 nearing the end of its contraction stroke,angle piece 124 which is part of the clamp member 18 engages plunger 122to close valve 118. This stops the feed of pressure fluid to ram 30, andbecause ram 38 is supplied with fluid to actuate it from ram 30 thisalso stops actuation of ram 38. The two rams in effect are hydraulicallylocked before any bottoming out of the ram for the trailing clamp memberoccurs.

The same type of operation occurs with side shifting to the right, wherecontrol valve 106 is adjusted to introduce pressure fluid to conduit 112with fluid exhausting through conduit 114. In this instance clamp member18 is the trailing clamp member, and ram actuation stops upon anglepiece 132 engaging plunger 130 to close valve 134.

The construction described is readily incorporated with clamp mechanism'such as is found in an attachment for a lift truck, with a minimumamount of hosing, etc., required to connect the multiple pilot checkvalve assembly with the valves 118, 130. Further, it is an easy matterwith the invention to mount the valves 118, 130 in a position wheretheir associated actuating members or plungers may properly sense whenthe trailing clamp member is in such a position that the ram for themember is near the end of its stroke.

What is claimed and desired to secure by letters patent:

l. In a clamp mechanism having a pair of opposed clamp members mountedon a frame for movement in the same direction on the frame to one or theother side thereof thus to side shift a load, one member leading and onemember trailing on such side shifting,

first bidirectional fluid-powered motor means con nected to one clampmember for moving it under power to one or the other side of the frame,said one clamp member moving as a trailing member with movement to oneside of the frame and said one clamp member and connected first motormeans being mechanically limited with respect to the movement affordedto said one side of the frame, a first sensing means for said one clampsensing independently of the position of the other clamp member apredetermined position of said one clamp member relativeto said frame,said predetermined position being proximate where inovement of said oneclamp member is mechanically limited,

second bidirectional fluid powered motor means connected to the otherclamp member for moving it under power to one or the other side of theframe, said other clamp member moving as a trailing member with movementto the other side of the frame and said other clamp memberand connectedsecond motor means being mechanically limited with respect to themovement afforded to said other side of the frame, a second sensingmeans for said other clamp member sensing independently of the positionof the one clamp member a predetermined position of said other clampmember relative to the frame, said predetermined position beingproximate where movement of said other clamp member is mechanicallylimited, and

valve means actuated by said first and second sensing means checkingmovement of the clamp members in response to either sensing meanssensing that its associated clamp member is in its said predeterminedposition. 1'

2. In clamp mechanism having a pair of opposed clamp members mounted ona frame for movement in the same direction on the frame, to one or theother side thereof, thus to side shift a load, one member leading andone member trailing on said side shifting,

a fluid-powered ram for each clamp member mounted on said frame andconnected to the clamp member whereby the clamp member is moved underpower on actuation of the ram, each ram including a cylinder and aninternal piston,

a source of fluid under pressure,

hydraulic circuit means connecting said source and said rams for thesupply and exhaust of fluid thereto and therefrom,

said circuit means including a first hydraulic system where the rams areconnected in parallel with said source and fluid under pressure isdirected to the rams to move the clamp members apart and move themtogether to effect the release and clamping of a load, said hydrauliccircuit further including a second hydraulic system wherein the'rams areconnected in series with fluid exhausting from one ram dumping into theother for the purpose of moving the clamp members to side shift a load,

said second system including a first valve on the feed side of both ramsactuated to produce side shifting to one side of the frame, a secondvalve on the feed side of the rams with the rams actuated to produceside shifting to the other side of the frame, each of said valves beingactuatable to stop the supply of pressure fluid to the rams thus to stopside shifting, each of said valves including a housing mounted on saidframe and having an actuator associated with the .valve for actuatingthe valve, part fixed to one clamp member to be movable solely withmovement of said one clamp member which moves against the actuator forone valve said one clamp member moving as a trailing member on sideshifting whereby the supply of pressure fluid to the rams is stopped,and a part fixed to the other clamp member to be movable solely withmovement of the other clamp member which moves against the actuator ofthe other valve with said other clamp member moving as a trailing memberon side shifting whereby the other valve is actuated to stop the supplyof pressure fluid to the rams. 3. The clamp mechanism of claim 1 whereinsaid valve means includes housing structure fixedly secured to saidframe, and the sensing means for each clamp member comprises an actuatorfor said valve means movably mounted in said housing structure and acooperating part fixed to the clamp member to be movable only withmovement of the clamp member in a path which brings said part intoengagement with said actuator.

4. In clamp mechanism having a frame and a pair of opposed clamp membersmovably mounted on the frame, each for movement toward one or the otherside of the frame, and a bidirectional fluid-powered motor for eachclamp member connected to the clamp member for moving it under power,one clamp member trailing the other on movement in unison of the clampmembers to a common side of the frame,

sensing means for sensing, independently of the position of the leadingclamp member and on movement of the clamp members to said common side ofthe frame, a predetermined position of the trailing clamp memberrelative to the frame, the trailing clamp member and its connected motorbeing mechanically limited with respect to the movement afforded to saidcommon side of the frame, said predetermined position for said trailingclamp member being proximate where movement of said trailing clampmember is mechanically limited,

a source of fluid under pressure,

and a hydraulic circuit connecting said source and said motor includingvalve means actuated by said sensing means to stop movement of bothclamp members in response to said sensing means sensing saidpredetermined position of said trailing clamp member.

1. In a clamp mechanism having a pair of opposed clamp members mountedon a frame for movement in the same direction on the frame to one or theother side thereof thus to side shift a load, one member leading and onemember trailing on such side shifting, first bidirectional fluid-poweredmotor means connected to one clamp member for moving it under power toone or the other side of the frame, said one clamp member moving as atrailing member with movement to one side of the frame and said oneclamp member and connected first motor means being mechanically limitedwith respect to the movement afforded to said one side of the frame, afirst sensing means for said one clamp sensing independently of theposition of the other clamp member a predetermined position of said oneclamp member relative to said frame, said predetermined position beingproximate where movement of said one clamp member is mechanicallylimited, second bidirectional fluid-powered motor means connected to theother clamp member for moving it under power to one or the other side ofthe frame, said other clamp member moving as a trailing member withmovement to the other side of the frame and said other clamp member andconnected second motor means being mechanically limited with respect tothe movement afforded to said other side of the frame, a second sensingmeans for said other clamp member sensing indepeNdently of the positionof the one clamp member a predetermined position of said other clampmember relative to the frame, said predetermined position beingproximate where movement of said other clamp member is mechanicallylimited, and valve means actuated by said first and second sensing meanschecking movement of the clamp members in response to either sensingmeans sensing that its associated clamp member is in its saidpredetermined position.
 2. In clamp mechanism having a pair of opposedclamp members mounted on a frame for movement in the same direction onthe frame, to one or the other side thereof, thus to side shift a load,one member leading and one member trailing on said side shifting, afluid-powered ram for each clamp member mounted on said frame andconnected to the clamp member whereby the clamp member is moved underpower on actuation of the ram, each ram including a cylinder and aninternal piston, a source of fluid under pressure, hydraulic circuitmeans connecting said source and said rams for the supply and exhaust offluid thereto and therefrom, said circuit means including a firsthydraulic system where the rams are connected in parallel with saidsource and fluid under pressure is directed to the rams to move theclamp members apart and move them together to effect the release andclamping of a load, said hydraulic circuit further including a secondhydraulic system wherein the rams are connected in series with fluidexhausting from one ram dumping into the other for the purpose of movingthe clamp members to side shift a load, said second system including afirst valve on the feed side of both rams actuated to produce sideshifting to one side of the frame, a second valve on the feed side ofthe rams with the rams actuated to produce side shifting to the otherside of the frame, each of said valves being actuatable to stop thesupply of pressure fluid to the rams thus to stop side shifting, each ofsaid valves including a housing mounted on said frame and having anactuator associated with the valve for actuating the valve, a part fixedto one clamp member to be movable solely with movement of said one clampmember which moves against the actuator for one valve said one clampmember moving as a trailing member on side shifting whereby the supplyof pressure fluid to the rams is stopped, and a part fixed to the otherclamp member to be movable solely with movement of the other clampmember which moves against the actuator of the other valve with saidother clamp member moving as a trailing member on side shifting wherebythe other valve is actuated to stop the supply of pressure fluid to therams.
 3. The clamp mechanism of claim 1 wherein said valve meansincludes housing structure fixedly secured to said frame, and thesensing means for each clamp member comprises an actuator for said valvemeans movably mounted in said housing structure and a cooperating partfixed to the clamp member to be movable only with movement of the clampmember in a path which brings said part into engagement with saidactuator.
 4. In clamp mechanism having a frame and a pair of opposedclamp members movably mounted on the frame, each for movement toward oneor the other side of the frame, and a bidirectional fluid-powered motorfor each clamp member connected to the clamp member for moving it underpower, one clamp member trailing the other on movement in unison of theclamp members to a common side of the frame, sensing means for sensing,independently of the position of the leading clamp member and onmovement of the clamp members to said common side of the frame, apredetermined position of the trailing clamp member relative to theframe, the trailing clamp member and its connected motor beingmechanically limited with respect to the movement afforded to saidcommon side of the frame, said predetermined position for said trailingclamp member being proximate where movement of said trailing clampmember is mechanically limited, a source of fluid under pressure, and ahydraulic circuit connecting said source and said motor including valvemeans actuated by said sensing means to stop movement of both clampmembers in response to said sensing means sensing said predeterminedposition of said trailing clamp member.